obsolete visna

Obsolete Visna: A Viral Infectious Disease

Obsolete visna, also known as ovine encephalomyelitis, was a viral infectious disease that affected sheep and goats. It resulted in infection located in the brain, causing severe symptoms.

• Transmission: The disease was transmitted through droplet spread of oronasal secretion, as well as by ingestion of contaminated water, milk, or colostrum [10].
• Symptoms: Early symptoms included unilateral hindlimb paresis, which is a condition where one leg becomes weak and paralyzed [5]. As the disease progressed, it caused encephalitis (inflammation of the brain) and chronic pneumonitis (inflammation of the lungs).
• Similarity to Scrapie: Obsolete visna was similar to but not the same as scrapie, another viral infectious disease that affects sheep [11].

Note: The term "obsolete" suggests that this disease is no longer a significant concern in modern veterinary medicine. However, it's essential to understand its historical significance and the impact it had on sheep and goat populations.

References:

[10] - A viral infectious disease that results_in infection located_in brain in sheep and goats... [5] - Symptoms Visna-maedi; The disease then [11] - It is similar to but not the same as scrapie. Ovine encephalomyelitis; obsolete visna.

Visna Disease Signs and Symptoms

Visna, also known as ovine progressive pneumonia (OPP), is a viral disease affecting sheep. The clinical signs and symptoms of visna can be divided into several categories:

• Respiratory Issues: Chronic pneumonia is a hallmark symptom of visna, leading to breathing difficulties or exercise intolerance in affected animals.
• Mastitis: Mastitis, an inflammation of the udder, is a common sign of visna, with both sides of the udder often being hard but not hot.
• Neurological Problems: Neurological signs such as a 'dragging' hindlimb gait or circling can occur in affected animals.
• Arthritis: Arthritis and wasting are also symptoms associated with visna.

The disease typically affects sheep aged 2 to 3 years, but can impact adults of any age. Transmission occurs through contact with infected animals or contaminated materials.

Incubation Period

The incubation period for visna is relatively long, with clinical signs often not appearing until several months after exposure. In some cases, affected animals may show no signs of illness at all, and are only discovered to be infected when they are found dead.

Age of Onset

Visna can affect sheep of any age, but the disease tends to appear somewhat sooner in younger animals. Clinical signs have been reported in sheep as young as 2 years old, although significant numbers of affected animals tend to be older than this.

References:

• [10] - Early Signs: The early signs of MV can be difficult to spot due to the slow progression of the disease.
• [13] - OPP, also known as maedi-visna, is a slow viral disease affecting sheep. It causes chronic pneumonia, leading to emaciation and wasting.
• [14] - Visna seems to appear somewhat sooner, with clinical signs in some sheep as young as 2 years.
• [15] - Maedi’ means ‘laboured breathing’ and describes the disease associated with a progressive interstitial pneumonitis.

Based on the available information, it appears that diagnostic tests for Maedi-visna viral infection have evolved over time.

Obsolete Diagnostic Tests

• Virus culture and virus isolation were once used to detect Maedi-visna virus, but these methods are no longer commonly used today [1].
• Electron microscopy was also employed in the past to diagnose this condition, although its use has been largely discontinued [2].

Current Diagnostic Methods

• Serological diagnostic testing using enzyme immunosorbent assays (ELISAs) is now the most common method for determining small ruminant lentivirus infection, including Maedi-visna virus [3].
• Other diagnostic techniques, such as antigen tests and PCR, may also be used to detect this virus.

Regulatory Requirements

• For official testing purposes, samples must be collected by an accredited veterinarian or laboratory personnel, and the test results must meet specific requirements set forth by regulatory agencies [4].

It's worth noting that diagnostic methods and regulations can vary depending on the country and region. If you have any further questions or would like more information on this topic, please let me know.

References: [1] Context result 1 [2] Context result 1 [3] Context result 2 [4] Context result 6

Visna Disease Treatment

Unfortunately, there are no effective treatment options available for visna disease in sheep. According to search results [14], the most common diagnostic methods used at present are combination ELISAs for Gag and Env proteins with virus variability making PCR less reliable.

Historically, researchers have explored various antiviral drugs as potential treatments for visna virus infection in sheep. For instance, a study published in 1995 [10] suggested that MVV infections could be used as an animal model for other Lentivirus infections such as HIV, and in the development of antiviral drugs.

However, no FDA-approved drug therapy is available for treating visna disease in sheep. Most work to find a treatment has involved only a few studies on antiretroviral drugs [15], but these have not been successful in developing an effective treatment.

Current Treatment Status

The current treatment status for visna disease is largely based on test and cull strategies, where infected animals are identified and removed from the flock to prevent further transmission. This approach can help control the spread of the disease but does not address the underlying infection.

In contrast to other diseases, there are no vaccination options available for visna disease in sheep [14]. The lack of effective treatment options makes it challenging to manage this disease, leading to significant production losses in affected flocks.

References

[10] Thormar, H., et al. (1995). MVV infections as an animal model for other Lentivirus infections such as HIV, and in the development of antiviral drugs.

[14] Maedi-visna (MV) is a lentiviral disease of sheep responsible for severe production losses in affected flocks.

[15] models (Naesens et al., 1994), it was concluded that visna virus infection in sheep can be used as an animal model for testing the effects of antiretroviral drugs on brain infections caused by lentiviruses, such as HIV-1.

Differential Diagnosis of Obsolete Visna

Obsolete visna, also known as maedi-visna, is a chronic disease of sheep caused by lentiviruses. When diagnosing this condition, it's essential to consider other diseases that may present similar symptoms. Here are some differential diagnoses for obsolete visna:

• Pulmonary adenocarcinoma: This type of cancer can cause respiratory problems and weight loss in sheep, making it a potential differential diagnosis for obsolete visna (Table 1) [13].
• Chronic pneumonia: A bacterial or viral infection that affects the lungs can lead to symptoms similar to those of obsolete visna, such as coughing and difficulty breathing [11].
• Lungworm infestation: Sheep infected with lungworms may exhibit respiratory problems, including coughing and difficulty breathing, which can be mistaken for obsolete visna [11].

Key Considerations

When attempting to diagnose obsolete visna, it's crucial to consider the following factors:

• Clinical presentation: The symptoms presented by the sheep, such as weight loss, coughing, and difficulty breathing, should be carefully evaluated.
• Laboratory tests: Blood samples can help identify the presence of lentiviruses or other pathogens that may be causing the disease [11].
• Epidemiological history: Understanding the epidemiology of the disease in the flock can provide valuable insights into the potential causes of obsolete visna.

References

[11] Ovine progressive pneumonia (OPP), or maedi-visna, is a chronic disease of sheep due to lentiviruses (enveloped, single-stranded RNA viruses in the family Retroviridae). The related disease in goats is referred to as caprine arthritis and encephalitis (CAE).

[13] Differential diagnosis. The principal diseases (Table 1) which can be confused with maedi-visna are pulmonary adeno- ... Table 1 Differential diagnosis of maedi-visna in sheep.

Note: The information provided above is based on the search results and context provided, and is intended to be informative and relevant to the user's query.